1. Technical Field
The present invention relates generally to encoder apparatus and methods, and, more particularly to encoder apparatus and methods for converting the cyclic motion of an electro-mechanical machine into meaningful electrical signals which can be used in a number of applications. One such application involves direct commutation of the electro-mechanical machine from which the encoder generated the electrical signal. An important field of such apparatus and methods concerns the control of electric motor operation.
2. Background Art
The most relevant background art to the present invention is found in the field of electric motor control and commutation. However, it is to be understood that the present invention is not limited to this field. Since the most important application of the present invention relates to the control of electric motor operation, the following discussion will relate primarily to this field.
In addition, most of the current applications of the present invention involve optical encoder implementations. However, it is to be understood that the present invention is not so limited. Since most current applications of the present invention concern optical encoding, the following disclosure will primarily address optical encoding and optical encoder embodiments.
The present invention may be implemented as a simple variable speed control device and method for A.C. motors which can additionally improve or enhance the motor's normal operating efficiencies. This implementation involves direct optical-to-electrical commutation of single and multi-phase A.C. induction motors, but also can be adapted for other A.C. and brushless D.C. motors.
Generally, commutation for A.C. induction motors involves using the A.C. power frequency to provide an induced current in the appropriate stator windings, creating a magnetic flux which, in turn, induces a current and resulting magnetic flux in the armature windings. When properly synchronized or matched, a torque or force is created between the two fluxes which causes the armature to move.
The motion of the armature, or motor speed, is directly proportional to the frequency of the input power at a specific voltage level. Normally A.C. motor input voltage and frequency are fixed, which in turn fixes the speed of the armature. In A.C. induction motors, a level of "frequency slip" is experienced between the stator and armature frequencies. That is, the speed of the armature is less than the speed of the stator's magnetic field. Control over the speed of the armature can be achieved by proper coordination of different frequencies, voltages, numbers of poles, numbers of windings or phases, amount of slip, etc.
Current methods of varying and controlling the speed of an A.C. motor (or brushless D.C. motor) usually involves some sort of motor-connected, speed sensing device that supplies feedback or input signals to a microprocessor, inverter or vector controller and driver, which are then analyzed, adjusted, varied, shaped, etc., to match frequency, voltage and power needs of the motor. The signal(s) from the microprocessor, inverter or vector drive, controls the frequency, power pulse widths, current and voltage amplitude(s), phasing(s) or various combinations of such parameters. These prior methods are generally complex, costly and cumbersome. They usually require a speed sensing input device or method, a separate analysis and control signal shaping unit, and a driver for power output, all of which must be properly connected and synchronized with each other.
The present invention differs from the above-mentioned methods by using a single device to sense, analyze and control speed as well as improve torque and power output, while using less energy. Similar to other methods, the present invention links motor speed to input power frequency and voltage, but accomplishes this link without most of the components used by other variable speed methods. The encoder of the present invention utilizes the novel concept of "optical programmability" to match, fit, profile and control, via direct commutation, the motor's speed, direction, slip, phasing, as well as improve torque and power while using less energy.
Others have disclosed methods of using optical encoders for D.C. electric motor commutation control. However, in these methods, the optical elements used--light emitters, detectors and encoder discs--could just as readily be resistive, magnetic or "electrically" varying elements. This is because these methods concern only one-dimensional optical "shuttering," i.e., merely diminishing and increasing light intensity, or blocking and unblocking the light path, to create either a sine wave or square wave output. Such waveforms could be similarly produced by non-optical elements.
The following patents disclose optical encoders employing a rotating encoder disc working in combination with a fixed disc, mask or reticle to produce a sinusoidal signal waveform: U.S. Pat. No. 3,193,744 to Seward; U.S. Pat. No. 4,160,200 to Imamura; U.S. Pat. No. 4,224,515 to Terrell; U.S. Pat. No. 4,429,267 to Veale; U.S. Pat. No. 4,599,547 to Ho; and U.S. Pat. No. 5,103,225 to Dolan et al. The following patents disclose the use of an optical encoder employing only an encoding disc or wheel, without a stationary mask or reticle, which produces square pulses for use in commutation and tachometer functions: U.S. Pat. No. 4,353,016 to Born; U.S. Pat. No. 4,882,524 to Lee; and U.S. Pat. No. 5,198,738 to Blaser et al. Finally, U.S. Pat. No. 5,177,393 to Webber discloses an optical encoder used for commutation of a D.C. brushless motor, employing a reflective encoder disc printed with a sinusoidal pattern.
All of the encoders disclosed in these patents are limited in that they cannot optically shape the waveform of the motor commutation signals to any desired form to optimize control of the motor's speed, direction, slip, phasing, torque and power output. In other words, they are not "optically programmable". In addition, many of the encoders proposed in these patents require additional commutation "control" components to produce square wave drive signals and match them to the poles and windings of the motor. Moreover, all of the above patented encoders depend on the physical placement, size, shape and interaction of all the optical elements. Finally, the encoders of these patents do not propose flexibility in design, or practical and affordable implementations.
The apparatus and methods of the present invention employ the optical encoder, itself, as an "optically programmable" device, which can directly sense, interpret and convert mechanical motion of a machine into programmed electrical signals that are compatible with the machine or with other control elements. The encoder is optically programmed, in that it implements a predetermined optical function and includes optical elements which can be graphically or geometrically shaped to represent almost any mathematical or algebraic waveform function. The encoder can produce at least one electrical signal having a predetermined waveform which is a transform of the optical function. Since the electrical signal is a direct result of the "cyclic" motion of the machine to which the encoder is coupled, it can be used to control (like a normal encoder), shape and enhance (like a microprocessor), modify and commutate (like a converter) and vary (like an amplifier). The term "cyclic," for the purposes of this application, is intended to include without limitation, recurring, repeating, periodic, rotating, reciprocating, and harmonic motion.
Optical programming includes the concept of "graphical programming". Graphical programming is the process of configuring encoder elements (e.g., an optical encoder disk) with graphically or geometrically shaped patterns or areas which are capable of being sensed during operation of the encoder. These graphically or geometrically shaped patterns or areas are defined by graphical functions (hereinafter described) which are, in turn, usually derived from mathematically or algebraically defined waveform functions (hereinafter described). In a preferred graphical programming procedure, the electrical signal to be created by the encoder is first specified. Then, a waveform function is determined and used to derive (e.g., by area-fill equations--described hereinbelow) a graphical function which, in turn, defines the graphically or geometrically shaped patterns or areas.
Graphical programming can be applied to any type of encoder in which the graphically shaped patterns or areas can be sensed. For example, capacitive encoders, such as those described in U.S. Pat. No. 5,172,039 to Owens and U.S. Pat. No. 4,864,300 to Zaremba, utilize conducting plates or patterns to produce variable capacitance between a rotating encoder element and a stationary encoder element. The variable capacitance is made part of an electrical circuit which produces the electrical signal output of the encoder. Such capacitive encoders could employ graphical programming, in that the stationary and rotating capacitive plates could be graphically or geometrically shaped. Such a capacitive embodiment would involve the multiplication of areas of at least two graphical or geometric shapes, co-defined by a graphical function. In another possible example, Hall Effect sensors may be used in combination with magnetic strips or patterns which are graphically or geometrically shaped.
It is the ability of the apparatus and methods of the present invention to create, shape, modify and control almost any mathematical or algebraic electronic output waveform pattern, via optical programming or graphical programming, that sets the present invention apart from methods and apparatus heretofore proposed.
3. Inventor's Perspective
My view, approach and perspective on encoders and encoding are very much analogous to electronics and electrical circuits. Specifically, I believe that optical encoding (OE) is at a similar threshold as integrated circuits (IC's) were for electronics some 30 to 40 years ago. IC's in many ways were merely repackaging of prior electronic circuits. This repackaging was initially nothing more than taking existing electronic circuits, components, etc. and integrating them into a single, smaller, more cost-effective usable device. However, that simple "repackaging" quickly evolved, and even revolutionized, not just the repackaging of existing circuits, but literally created new markets, industries, and electronic circuits. Many of such circuits were only conceptualized or mathematically represented prior to the IC, and in some cases not even conceived. Yet such circuits were made possible by this "repackaging" or consolidating into a single product approach.
I believe that my approach to encoding methods, specifically optical encoding, stands at a similar threshold. There are various optical encoding techniques in existence today, but the "repackaging" into a single or miniaturized cost-effective, compact product, as my generic approach does, affords similar scenarios of possibilities.
To further illustrate the analogy, I have now developed in a single OE package, an "optical programming" method that has given optical encoding new application possibilities never heretofore utilized or, in some cases, even envisioned by this "single product method".
Like the IC, in some cases, many of these applications already existed in other forms or with other multiple components. My method and approach has consolidated these into a singular product. However, as with IC's, I have also been able to reduce to practice concepts only heretofore mathematically represented, or which could never be affordably or practically constructed.
Further, I believe that I have likewise created and invented additional new concepts and applications never heretofore explored or contemplated prior to my new "IC approach". This "optical programmability" (op) that I have developed in connection with an optical encoder (OE) can be likened to a type of microprocessor (micro or .mu.p), in that a micro is a unique series of electronic circuits, representing various capabilities, adaptability, and "programmability" oftentimes on a single IC chip.
I have likewise developed "programmability" or various application capabilities and processing abilities like a .mu.p or micro, but consolidated into a single cohesive package (like an IC). It is this novel, unique concept of equating the encoder, optical encoding, optical programming, generic capability into one package, that makes my method analogous to the integrated circuit and micro. As the IC helped to evolve and create the micro which in turn opened up new concepts of electronic applications, and capability, and even industries, so may/should optical encoding and optical programmability.
It is thus my contention that the present invention and concept of optical encoding and optical programming stand where integrated circuits and microprocessors stood some 30 to 40 years ago. The extent and range of the capabilities, possibilities, products, and industries are only just now being slightly scratched by my approach.
It is this ubiquitous, generic expectation that I have for optically programmed encoders that makes this concept and product so exciting, unique and limitless in possibilities.